Mechanisms underpinning sympathetic nervous activity and its modulation using transcutaneous vagus nerve stimulation

Figures

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  Figure 1. Sympathetic and heart rate responses to chemoreceptor or noxious stimulation are blunted in the connexin 36 knockout (KO) mouse Each panel shows the raw data, obtained using the working heart–brainstem preparation, with sympathetic nerve discharge (SND), integrated sympathetic nerve activity (∫SND) and perfusion pressure (pp) and the mean data for integrated sympathetic nerve discharge. Sympathoexcitation upon chemoreceptor stimulation or noxious pinch (arrow denotes point of stimulation) is significantly reduced in Cx36 KO mice compared with wild‐type. Adapted from Lall et al. (2017), with permission.

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  Figure 2. Relationship between low‐frequency to high‐frequency (LF/HF) ratio and effects of transcutaneous vagus nerve stimulation A, plotting the baseline LF/HF ratio against age shows a significant relationship between these parameters (R 2 = 0.19; P = 0.013). B, there is a relationship between baseline LF/HF ratio and change in LF/HF ratio during transcutaneous vagus nerve stimulation, indicating that higher LF/HF ratios predict a greater decrease in LF/HF during transcutaneous vagus nerve stimulation (R 2 = 0.58; P < 0.0005). Adapted with permission from Clancy et al. (2014).

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  Figure 3. Potential pathways involved in cardiovascular responses elicited by stimulation of the tragus The pathways in green represent the potential afferent inputs to the CNS, with the dotted lines being those under investigation. Red pathways are interneurones involved in the autonomic modulation, while vagal efferent pathways are in orange and the sympathetic components of the pathways are in blue. Abbreviations: Pa5, paratrigeminal nucleus; DVN, dorsal vagal motor nucleus; NA, nucleus ambiguus; RVLM, rostral ventrolateral medulla; CVLM, caudal ventrolateral medulla; DH, dorsal horn; IML, intermediolateral cell column; SA Node, sinoatrial node.